The disclosure of Japanese Patent Application No. 2001-278761 filed on Sep. 13, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to a fluid-filled active vibration-damping device, which has a primary fluid chamber filled with a non-compressible fluid, and which is capable of actively offsetting or reducing vibrations applied to the primary fluid chamber by controlling a fluid pressure in the primary fluid chamber. More particularly, the present invention is concerned with a pneumatically operated fluid-filled active vibration-damping device wherein the fluid pressure in the primary fluid chamber is controlled by means of an air pressure applied thereto from the external area, and an active vibration-damping apparatus equipped with the same, which is suitably applicable to an active elastic mount and an active dynamic damper or oscillator for use in automotive vehicles, for example.
2. Description of the Related Art
Vibration-damping devices have been used for damping or isolating vibrations (including noises induced by the vibrations) of a subject member such as a body of an automotive vehicle or other members suffering from these vibrations or noises. Known examples of such vibration-damping devices include: a vibration-damping coupling or mount, e.g., an engine mount, which is interposed between the subject member and a vibration source, e.g., a power unit, so as to connect these two members in a vibration-damping fashion for eliminating or reducing a vibration transmitted from the vibration source to the subject member; and a vibration damper that is fixed to the subject member for absorbing or reducing the vibration of the subject member.
A fluid-filled active vibration-damping device has been proposed as one type of such vibration-damping devices, as disclosed in JP-A-10-184769. The known fluid-filled active vibration-damping device includes: an elastic body elastically deformed due to vibrational loads applied thereto; a primary fluid chamber partially defined by the elastic body and an elastically displaceably movable member, while being filled with a non-compressible fluid; and a working air chamber formed on one side of the movable member that is remote from the other side on which the primary fluid chamber is formed. The pressure of the fluid in the primary fluid chamber varies due to the elastic deformation of the elastic body upon application of the vibrational loads to the elastic body, and is also actively controllable by applying a suitable air pressure variation to the working air chamber from the external area, which is transmitted to the primary fluid chamber via the movable member. Such a known fluid-filled active vibration-damping device is capable of actively controlling a fluid pressure variation induced in the primary fluid chamber by applying an air pressure variation corresponding to a vibration to be damped, thereby exhibiting an active vibration-damping effect or an offsetting effect with respect to vibrations excited in the subject member to which the fluid-filled active vibration-damping device is installed.
In order to induce a suitable air pressure variation in the working air chamber, the known fluid-filled active vibration-damping device generally employs a vacuum source such as a negative pressure available from an air intake part of an internal combustion engine and an atmosphere as pressure sources, and a solenoid-operated switch valve operable for alternately connecting and disconnecting the working air chamber to and from the vacuum source and the atmosphere at a frequency corresponding to that of vibrations to be damped. However, the known fluid-filled active vibration-damping device is incapable of confirming a waveform of the air pressure variation induced in the working air chamber to a waveform of amplitude of vibrations to be damped, causing undesirable generation of higher harmonic components of a primary frequency of the air pressure variation generated in the working air chamber. The higher harmonic components are undesirably transmitted to the primary fluid chamber, causing deterioration of a vibration-damping capability of the fluid-filled active vibration-damping device.
To cope with the above-mentioned conventional problem, the present assignee has disclosed in JP-A-11-82611 an improved fluid-filled active vibration-damping device in which a resonance pipe or the like is connected to a portion of an air piping system provided for applying the air pressure variation to the working air chamber, for the purpose of reducing or attenuating the higher harmonic components included in the air pressure variation.
However, extensive studies conducted by the present inventors has revealed that the improved fluid-filled active vibration-damping device needs to branch a pipe in the air piping system with a branch pipe or the like for disposing the resonance pipe on the portion of the air piping system, or to form a special port in the solenoid-operated switch valve in order to connect the resonance pipe to the solenoid-operated switch valve, thus deteriorating efficiency in manufacturing the air piping system. Also, additional spaces are required on the air piping system for an installation such a branch pipe, a special port and the like, making it difficult to install the improved fluid-filled active vibration-damping device on any automotive vehicle by simply changing the design of the vibration-damping device.
In addition, even if the resonance pipe is disposed on the portion of the air piping system, the fluid-filled active vibration-damping device may still possibly suffer from generation of the higher harmonic components in the air pressure variation transmitted through the air piping system, due to the presence of bending or narrowed portions in an air passage of the air piping system located between the portion at which the resonance pipe is connected to the pipe in the air piping system and the working air chamber. That is, the improved fluid-filled active vibration-damping device is not able to cope with the problem of such higher harmonic components in the air pressure variation, leaving some room for improvement.
It is therefore an object of the present invention to provide an improved pneumatically operated fluid-filled active vibration-damping device, which is capable of eliminating or minimizing generation of higher harmonic components of a primary frequency of an air pressure variation in the working air chamber while simplifying the structure of the damping device and eliminating a need for a special modification to an air piping system, and accordingly which is capable of exhibiting a desired active vibration-damping effect with high stability.
The above and/or other objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A pneumatically operated fluid-filled active vibration-damping device comprising: (a) an elastic body elastically deformed due to vibrational loads applied thereto; (b) a primary fluid chamber partially defined by the elastic body and filled with a non-compressible fluid; (c) a movable member being elastically displaceable and partially defining the primary fluid chamber on one of opposite sides thereof; (d) a working air chamber disposed an other one of opposite sides of the movable member; and (e) an air reservoir directly extending from the working air chamber and fluid-tightly closed at a protruding end portion thereof; wherein a fluid pressure variation in the primary fluid chamber is induced by an elastic deformation of the elastic body while being actively controlled by transmitting an air pressure variation applied to the working air chamber from an external area to the primary fluid chamber via the movable member.
In the pneumatically operated fluid-filled active vibration-damping device according to the present mode of the invention, the air reservoir is formed so as to directly extend from the working air chamber of the vibration-damping device. This arrangement eliminates a need to modify an air piping system provided outside the vibration-damping device for applying the air pressure variation to the working air chamber. That is, the present pneumatically operated fluid-filled active vibration-damping device is capable of reducing or attenuating higher harmonic components of a primary frequency of the air pressure variation in the working air chamber based on a resonance effect of the air reservoir, without needing a design change of the air piping system or an increased space for installing the air piping system.
In addition, the air reservoir is directly open to the working air chamber in the pneumatically operated active fluid-filled vibration-damping device of this mode of the invention, thus making it possible to more efficiently reduce the higher harmonic components of the primary frequency of the pressure variation induced in the working air chamber, in comparison with the above-mentioned conventional case where the resonance pipe or the like is connected to a portion of the air piping system provided outside of the vibration-damping device.
(2) A pneumatically operated fluid-filled active vibration-damping device according to the above-indicated mode (1), wherein a wall of the working air chamber is formed with a first outlet adapted to be connected with a closed tubular pipe for forming the air reservoir, and a second outlet_adapted to be connected with an air piping system for applying the air pressure variation to the working air chamber. According to this mode of the invention, the use of the closed tubular pipe makes it possible to form the air reservoir having a longitudinal configuration, with ease. For instance, the air reservoir may have a desired effective length by simply replacing the closed tubular pipe. Preferably, a pocket having a volume smaller than that of the working air chamber is formed to be open in a portion of the wall of the working air chamber, and the first and second outlets are formed at respective portions of the pocket. This arrangement ensures that the higher harmonic components in the air pressure variation to be applied to the working air chamber are effectively reduced or attenuated within the pocket based on the resonance effect of the air reservoir, before the higher harmonic components are transmitted to the entire of the working air chamber.
(3) A pneumatically operated fluid-filled active vibration-damping device according to the above-indicated mode (1) or (2), wherein the movable member has an elasticity by which the movable member is restored to an initial shape thereof. According to this mode of the invention, the movable member may be a plate member formed of a rubber elastic body with a given thickness, for example. This makes it easy to dispose in position the movable member while ensuring a fluid-tightness of the primary fluid chamber, and facilitates the oscillation of the movable member by alternately apply the negative pressure and the atmospheric pressure to the working air chamber.
(4) A pneumatically operated fluid-filled active vibration-damping device according to any one of the above-indicated modes (1)-(3), wherein the primary fluid chamber includes a pressure-receiving chamber partially defined by the elastic body and an oscillating chamber partially defined by the movable member, the pressure-receiving chamber and the oscillating chamber are held in fluid communication with each other via an orifice passage. According to this mode of the invention, the fluid pressure variation in the oscillating chamber, caused by the oscillation of the movable member as a result of the air pressure variation induced in the working air chamber, is efficiently transmitted to the pressure-receiving chamber with the help of resonance of the fluid flowing through the orifice passage. Therefore, the fluid pressure variation in the pressure-receiving chamber can be efficiently controlled.
(5) A pneumatically operated fluid-filled active vibration-damping device according to any one of the above-indicated modes (1)-(4), further comprising a first mounting member and a second mounting member that are elastically connected with each other via the elastic body, wherein the first mounting member is adapted to be attached to a vibrative member and the second mounting member is adapted to be attached to a subject member whose vibrations to be damped so that the vibration-damping device is interposed between the vibrative member and the subject member for elastically connecting the vibrative member and the subject member in a vibration-damping fashion. The pneumatically operated fluid-filled active vibration-damping device according to this mode of the invention can provide effectively vibration-damping devices for use in an automotive vehicle, such as an engine mount, a differential mount, a body mount, a suspension mount and a suspension bushing.
(6) A pneumatically operated fluid-filled active vibration-damping device according to the above-indicated mode (5) wherein the elastic body has a generally frusto-conical shape and is bonded at a small diameter end portion thereof to the first mounting member, and the second mounting member having a cylindrical portion, while one of axially opposite open ends of the cylindrical portion of the second mounting member is bonded to an outer circumferential surface of a large diameter end portion of the elastic body to be fluid-tightly closed, and an other one of axially opposite open ends of the cylindrical portion of the second mounting member is fluid-tightly closed by a flexible diaphragm elastically deformable, the vibration damping device further comprising: a partition member fixedly disposed within a bore of the cylindrical portion of the second mounting member such that the partition member extends in a radial direction perpendicular to an axis of the cylindrical portion so as to form the primary fluid chamber partially defined by the elastic body on one of opposite sides thereof and an auxiliary fluid chamber whose volume is variable partially defined by the flexible diaphragm and filled with the non-compressible fluid on an other one of opposite sides thereof; and a fluid passage for permitting a fluid communication between the primary fluid chamber and the auxiliary fluid chamber, wherein the partition member includes a recess open to the primary fluid chamber and being closed by the movable member so as to form the working air chamber on one of opposite sides of the movable member, which is remote from the primary fluid chamber, the air piping system and the air reservoir being open in an inner surface of the recess of the partition member. According to this mode of the invention, the primary fluid chamber partially defined by the elastic body and the movable member, and the working air chamber partially defined by the movable member, are made simple in construction and are formable with ease. Moreover, the vibration-damping device according to this mode of the invention can exhibit a passive damping effect with the help of resonance of the fluid flowing through the fluid passage due to the pressure difference between the primary and auxiliary fluid chambers, with respect to vibrations within a specific vibration range.
(7) A pneumatically operated fluid-filled active vibration-damping device according to the above-indicated mode (6), wherein the partition member includes a first groove open in an outer circumferential surface thereof, and an opening of the first groove is closed by the cylindrical portion of the second mounting member so as to at least partially form the air reservoir. This arrangement makes it possible to form at least partially the air reservoir within the cylindrical portion of the vibration-damping device. Namely, the air reservoir can be formed, while preventing enlargement of the vibration-damping device itself and its installation space.
(8) A pneumatically operated fluid-filled active vibration-damping device according to the above-indicated mode (7), wherein the partition member further includes a second groove open in an outer circumferential surface thereof and independent of the first groove, and an opening of the second groove is fluid-tightly closed by the cylindrical portion of the second mounting member so as to form the fluid passage. According to this mode of the invention, the fluid passage as well as the air reservoir can be formed within the cylindrical portion of the second mounting member of the vibration-damping device, with high space utilization.
(9) A pneumatically operated fluid-filled active vibration-damping device according to any one of the above-indicated modes (1)-(4), further comprising a support member and a mass member that are elastically connected with each other via the elastic body, the support member being adapted to be attached to a subject member whose vibrations to be damped such that the mass member is elastically supported by the subject member via the elastic body. According to this mode of the invention, the elastic body as a spring component and the mass member as a mass component cooperate to form one vibration system. An application of the air pressure variation to the working air chamber causes oscillation of this vibration system, and the resonance of this vibration system is effectively utilized to apply an oscillating force corresponding to the vibrations to be damped to the subject member, so that the vibration-damping device capable of offsetting or actively damping vibrations is effectively provided.
(10) A pneumatically operated fluid-filled active vibration-damping device according to any one of the above-indicated modes (1)-(9), further comprising a shutoff mechanism for inhibiting a connection of the air reservoir to the working air chamber. This arrangement makes it possible to substantially eliminate the air reservoir depending upon vibration conditions of the subject member whose vibrations to be damped, objects of vibration damping, or the like. For instance, the shutoff mechanism may be operated to eliminate the air reservoir, when the air pressure variation is not applied to the working air chamber, or alternatively when the higher harmonic components of the primary frequency of the air pressure variation induced in the working air chamber is not concerned. Therefore, the shutoff mechanism is operable to prevent unnecessary increase in a volume of the working air chamber due to the presence of the air reservoir, as needed, e.g., for restricting the passive displacement of the movable member as a result of the fluid pressure variation in the primary fluid chamber, or alternatively for improving a response upon controlling the air pressure in the working air chamber.
(11) A pneumatically operated fluid-filled active vibration-damping apparatus comprising: a pneumatically operated fluid-filled active vibration-damping device defined in any one of the above-indicated modes (1)-(10) of the invention; an external air piping system independent of the vibration-damping device and connected to the working air chamber of the vibration-damping device in order to apply the air pressure variation to the working air chamber from an external area; a switch valve disposed on the air piping system and operable for alternately connecting the working air chamber to two pressure sources having different pressure values for generating the air pressure variation in the working air chamber. According to this mode of the invention, the air reservoir is effectively formed without needing a specific modification of the air piping system e.g., providing a branch pipe on the external air piping system, or undesirable increase in a required installation space of the air piping system. Thus, the vibration-damping apparatus according to this mode of the invention is applicable with ease to existing vibration-damping apparatus, for thereby assuring an improved vibration-damping effect.